Thyroid carcinoma showing thymus-like differentiation: Case presentation of a young man.

Ectopic thymic tissue can be present in the thyroid gland and a carcinoma showing thymus-like differentiation (CASTLE) may arise from such tissue. We are reported the case of a 26-year-old man with CASTLE, with cervical subcutaneous nodules relapse, who showed a good response to treatment with surgery, chemotherapy and radiotherapy. The problematic aspect of this case was the diagnosis; only on review were we able to make a final diagnosis. CASTLE is a very rare neoplasm. It is important to differentiate this cancer from others tumors such as primary or metastatic squamous cell carcinoma of the head and neck or squamous cell thyroid carcinoma, because the therapy and prognosis are different. Diagnosis is complicated and requires careful histological analysis (CD5- and P63-positive with presence of Hassall's corpuscles); unfortunately there is no gold standard treatment so, in this case, we administered a sandwich of chemotherapy and radiotherapy.